In the manufacture of packaged integrated circuit chips, the packaged chips are placed in a socket of a test fixture for testing. The packages have an array of connection bumps or balls on one side. The socket has an array of pins that connect to the bumps or balls when the package is placed into the socket. The test fixture applies signals to some of the pins and receives signals from other pins to perform a variety of different tests. Some packages have connectors on the top of the package as well as on the bottom. To test such a package some test fixtures have an upper plate with another set of pins that is attached over the package after the package is mounted in the bottom socket.
In package testing, it is important that the package be properly aligned so that the proper bumps or balls connect with the intended pins. Technology is trending to smaller solder bump pitch sizes. The bump pitch refers to the number of bumps in a particular amount of space on a connection surface of the package. As the pitch increases, the bumps are closer together. Bump pitch is increasing in order to increase the number of connections and to reduce the size of the integrated circuit packages. The smaller and more numerous connections make it more difficult to properly mount a package in a socket.
In many sockets, the integrated circuit chip package is aligned to the socket using the edge of the package as a mechanical reference. As the package is dropped into the socket, its edge follows a chamfered surface that guides the package into place.